package pipeline.vertex;

import javax.vecmath.Color3f;
import javax.vecmath.Vector2f;
import javax.vecmath.Vector3f;

import pipeline.Pipeline;
import pipeline.misc.Vertex;

/**
 * This class is a wrapper for the code that does triangle processing -- or
 * vertex processing, in the more traditional pipeline terminology. Its mission
 * is to transform a triangle into screen space vertex coordinates for the
 * rasterizer and to translate the vertex attributes supplied by the caller into
 * a set of attributes that will provide the necessary information for the
 * fragment processing stage.
 */
public abstract class VertexProcessor {
	
	/** A list of valid Triangle Processors */
	public static Class[] classes = { 
		ConstColorVP.class, 
		SmoothShadedVP.class, 
		TexturedSmoothShadedVP.class, 
		FragmentShadedVP.class, 
		TexturedFragmentShadedVP.class 
		};
	
	/**
	 * Returns the number of attributes this triangle processor will provide.
	 * 
	 * @return The number of attributes this triangle processor will provide.
	 */
	public abstract int nAttr();
	
	/**
	 * We can access everything we need to know about the pipeline state -- the
	 * current transformation matrices and the lighting parameters -- via the
	 * Pipeline reference above. But for efficiency we may want to do some
	 * precomputation. This function will be called by the pipeline to notify this
	 * object whenever the transforms parameters are changed.
	 * 
	 * @param pipe The reference to the pipeline object. Can be used to determine
	 *          the necessary matrices.
	 */
	public abstract void updateTransforms(Pipeline pipe);
	
	/**
	 * We can access everything we need to know about the pipeline state -- the
	 * current transformation matrices and the lighting parameters -- via the
	 * Pipeline reference above. But for efficiency we may want to do some
	 * precomputation. This function will be called by the pipeline to notify this
	 * object whenever the lighting parameters are changed.
	 * 
	 * @param pipe The reference to the pipeline object. Cna be used to determine
	 *          the viewing conditions.
	 */
	public void updateLightModel(Pipeline pipe) { }
	
	/**
	 * This is the main function of this class, which is called once for every
	 * triangle in the scene. As input we get all the attributes of the triangle's
	 * three vertices, and as a result this function should call the rasterizer
	 * with appropriate vertex positions and attribute values.
	 * 
	 * @param v The three vertices in 3D object coordinates.
	 * @param c Colors associated with each of the vertices.
	 * @param n A normal for each vertex.
	 * @param t Texture coordinates for each vertex.
	 * @param output The array of 3 vertices that serves as the output for this
	 *          method.
	 */
	public abstract void triangle(Vector3f[] v, Color3f[] c, Vector3f[] n, Vector2f[] t, Vertex[] output);
	
	/**
	 * This is the main function of this class, which is called once for every
	 * vertex. This routine takes the provided vertex data and prepares a 
	 * transformed vertex with attributes, ready to be sent to the rasterizer.
	 * 
	 * @param v The vertex position in 3D object coordinates.
	 * @param c The color associated with the vertex (null if unused).
	 * @param n The vertex normal (null if unused).
	 * @param t Texture coordinates for each vertex (null if unused).
	 * @param output The processed vertex.
	 */
	public abstract void vertex(Vector3f v, Color3f c, Vector3f n, Vector2f t, Vertex output);
	
}